Agricultural combines are large machines that harvest, thresh, separate and clean agriculturally raised crops bearing grain. The clean grain obtained is stored in a grain tank arranged on the combine. The threshed straw is generally either chopped and spread out on the field across the width of the chopping mechanism, or diverted around the straw chopper and deposited unchopped in a swath in order to be subsequently taken up in a bailer. The remaining crop residue at the rear outlet of the cleaning device, such as chaff and small pieces of straw, is distributed on the field by a chaff scattering device, or directed through the straw chopper and spread on the field.
DE 19908111 C1 describes a combine with a straw chopper and two impeller blowers following the straw chopper, arranged one alongside the other, for strewing the straw widely across the field. For the purpose of a material transfer that does not change direction, the outlet of the straw chopper and the inlet of the impeller blowers, which are arranged in a housing and have throw paddles rotating about a roughly vertical axis, are arranged in a single plane. Sheaths that join one another between the impeller blowers in a tip pointing towards the straw chopper are arranged around the impeller blowers. In the rear area, the sheaths are broken out in order to emit the straw onto the field. There is a covering above the impeller blower, while no cover is present on its underside.
A combine with a straw chopper is described in US 2007/0015556 A1 in which the outlet of the straw chopper acts from below at an acute angle on the downstream impeller blowers. There is a covering above the impeller blower, while no cover is present on its underside.
DE 10 2007 037 485 B3 shows a combine in which the straw chopper emits the crop residues in free flight and acts on the impeller blowers axially at an acute angle.
WO 2008/156419 A1 describes a similar arrangement of the straw chopper and impeller blower, but the crop flow is diverted downstream of the straw chopper by a deflection plate so that it strikes the impeller blower axially, but at a relatively acute angle. The central part of the crop residue flow is less strongly deflected than the outer part, in order that the velocity existing after the residue leaves the chopper is utilized to the best extent possible, in that the impeller blowers turning inwards with their front sides are acted on by the outer part of the crop residue flow in front of the axis of rotation, while the central part of the crop residue flow is thrown against the impeller blowers in the area behind the axis of rotation. The impeller blowers are arranged in housings that are open, apart from the deflection plates, on their axial end face where they are loaded, and are closed at the other end face.
In the above-mentioned prior art, the impeller blowers comprise throw paddles, mounted on central shafts, whose leading surfaces are flat and extend radially outwards up to the edge of the impeller blower and axially over the entire length of the shaft. In each case, a number of throw paddles are distributed around the shaft.
While relatively large gaps remain between the outlet of the straw chopper and the impeller blowers, through which the air conveyed by the straw chopper out of the interior of the combine and in particular, the air coming from the cleaner, can escape to the outside in the impeller blowers according to DE 19908111 C1, US 2007/0015556 A1 and DE 10 2007 037485 B3, this air must all be conveyed by the throw paddles in the impeller blowers according to WO 2008/156419 A1, since the crop flow is guided by the deflection plates between the straw chopper and the impeller blowers and no gap to the outside remains. This often results in conveyance problems, because the crop residues are not always removed in the desired manner due to the high air pressure that builds up at the inlet to the impeller blower. The high air pressure can spread to the cleaning device of the combine and result in unsatisfactory performance there as well.